The effects of hyperinsulinemia on the structure and performance of the myocardium in premature infants requiring intravenous hyperalimentation will be studied. Circulating insulin levels in premature infants who develop Hypertrophic Cardiomyopathy will be examined. Premature infants receiving high caloric concentrations of parenteral nutrition alone as well as those requiring exogenous insulin infusion along with hyperalimentation will be studied.